Potent AChE Inhibitor Research Articles

Synthesis and Characterization of Novel Heteroarylacrylonitrile Derivatives Containing Pyrazole Scaffold

2,3-disubstituted acrylonitriles derivatives are among the most important molecules in medicinal chemistry due to their bioactivity and their role as starting compounds for many bioactive molecules. Many heterocyclic structures have been investigated as AChE enzyme inhibitors. Nowadays, E/Z acrylonitrile derivatives are being studied as new AChE inhibitors. This study aimed to synthesis new heteroaryl-acrylonitrile compounds using Knoevenagel condensation. In this context, acrylonitrile compounds with aryl and heteroaryl structures at positions 2 and 3 (respectively )were synthesized from the reactions of pyrazole aldehyde derivative (4) with various acetonitrile compounds. Synthesized novel heteroarylacrylonitrile derivatives (5a-d) containing pyrazole ring are potential AChE inhibitors. The structures of the synthesized compounds were elucidated by FTIR, 1H-NMR and 13C-NMR spectroscopic techniques.

Synthesis, biological evaluation, and computational studies of N-benzyl pyridinium–curcumin derivatives as potent AChE inhibitors with antioxidant activity

A library of N-benzylpyridinium-based compounds, 7a-j and 8a-j, was designed and synthesised as potential acetylcholinesterase) AChE (inhibitors. An in vitro assay for the synthesised compounds showed that most compounds had significant AChE inhibitory activities at the nanomolar and submicromolar levels. The benzyl (8a) and fluoro (8b) derivatives were the most active, with IC50 values ≤56 nM. Compound 7f, which had a benzyl moiety, showed the highest potency among all the target compounds, with an IC50 value of 7.5 ± 0.19 nM against AChE, which was higher than that of the activities of tacrine (IC50 = 30 ± 0.2 nM) and donepezil (IC50 = 14 ± 0.12 nM). Compounds with vanillin moieties exhibited antioxidant activity. Among the tested compounds, four derivatives (7f, 7 g, 8f, and 8 g) exhibited superior AChE inhibitory activity, with K i values of 6–16 nM, which were potent in the same range as the approved drug, donepezil. These compounds showed moderate antioxidant activities, as indicated by the results of the ABTS assay.

Design, synthesis, biological evaluation, and molecular docking of euparin and 2‑hydroxy acetophenone hydrazone derivatives as potential AchE inhibitors

Euparin and 2‑hydroxy acetophenone hydrazone derivatives (2–7) were synthesized, and their structure was characterized by Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (NMR), and Mass (MS) spectral data. In vitro, using a modified Ellman's spectrophotometric approach, the inhibitory potential of these substances on the AchE (Acetylcholinesterase) enzyme was determined. Compounds 3, 5, and 7 exhibited strong and specific inhibitors of AchE. Ortho hydroxy acetophenone hydrazones were less effective than the euparin-based compounds 5 and 7, with an IC50 of 22 nM and 14 nM, respectively. The highest AchE inhibitory activity was seen in compound 7, which was close to what was observed for the reference drug, Donepezil. To further investigate the potential interactions between these chemicals and AchE, docking tests were conducted. A link between the biological, electronic, and physicochemical credentials of the compounds in the title was established through structure-activity relationships and in silico ADME studies. Molecular docking simulation disclosed that the highest docking scores were -9.96 and -10.77 kcal/mol for compounds 5 and 7, respectively. Further, the antibacterial and antifungal activity of samples 1–7 were evaluated against Candida albicans, Gram-positive and Gram-negative bacteria.

Synthesis, Molecular Docking and Molecular Dynamic Studies of Thiazolidineones as Acetylcholinesterase and Butyrylcholinesterase Inhibitors

Neurodegenerative diseases are chronic, progressive, age-related, and characterized by the loss of function of neurons caused by the accumulation of free radicals and oxidative stress. Although the prevalence of neuro disorders is rising, therapeutic efficacy is still limited due to various variables, including the blood-brain barrier. Hence, to identify molecules targeting different enzymes like acetylcholinesterase, butyrylcholinesterase and peroxiredoxins, a series of thiazolidineone derivatives were designed and synthesized. Schiff base was synthesized and cyclised with thioglycolic acid to yield thiazolidineones (T1-T10). Structural characterization was performed by IR, Mass and 1H NMR spectral studies and then subjected to in silico analysis against acetylcholinesterase (6O4W) and butyrylcholinesterase (1P0P). Compound T-9 (–10.10 kcal/mol) and T-8 (–7.65 kcal/mol) have shown excellent binding with 6O4W and 1P0P, respectively, compared with other derivatives. In addition, the compounds were checked for antioxidant activity by analyzing the interactions with peroxiredoxins (1URM), and compound T-4 was active. According to the physicochemical and ADME properties of Qikprop, synthesized compounds can be considered druglike molecules. In vitro, acetylcholinesterase inhibitory activity reveals compound T-8 as the most potent AChE inhibitor. In vitro, antioxidant activity found that compound T-4 has significant antioxidant activity. The compound T-8, with better docking scores and decisive acetylcholinesterase inhibitory action, was further explored to validate the molecular interactions through molecular dynamics studies. It was observed that compounds with the benzyl sulfonyl group (T-6 to T-10) showed higher AChE inhibitory potency than derivatives with phenyl substituents in place of the benzyl sulfonyl group (T-1 to T-5). Therefore, it is inferred that the sulfonyl group and substituents at the para position are essential for the higher inhibitory activity of compounds. Thus, there is plenty of scope for further study in developing these as promising lead compounds.

Repurposing of FDA-approved drugs as dual-acting MAO-B and AChE inhibitors against Alzheimer's disease: An in silico and in vitro study

An in silico consensus molecular docking approach and in vitro evaluations were adopted in the present study to explore a dataset of FDA-approved drugs as novel multitarget MAO-B/AChE agents in the treatment of Alzheimer's disease (AD). GOLD 5.3 and Glide were employed in the virtual assessments and consensus superimpositions of the obtained poses were applied to increase the reliability of the docking protocols. Furthermore, the top ranked molecules were subjected to binding free energy calculations using MM/GBSA, Induced fit docking (IFD) simulations, and a literature review. Consequently, the top four multitarget drugs were examined for their in vitro MAO-B and AChE inhibition effects. The consensus molecular docking identified Dolutegravir, Rebamipide, Loracarbef and Diflunisal as potential multitarget drugs. The biological data demonstrated that most of the docking scores were in good correlation with the in vitro experiments, however the theoretical simulations in the active site of MAO-B identified two false-positives – Rebamipide and Diflunisal. Dolutegravir and Loracarbef were accessed as active MAO-B inhibitors, while Dolutegravir, Rebamapide and Diflunisal as potential AChE inhibitors. The antiretroviral agent Dolutegravir exhibited the most potent multitarget activity - 41% inhibition of MAO-B (1 μM) and 68% inhibition of AChE (10 μM). Visualizations of the intermolecular interactions of Dolutegravir in the active sites of MAO-B and AChE revealed the formation of several stable hydrogen bonds. Overall, Dolutegravir was identified as a potential anti-AD drug, however further in vivo evaluations should be considered.

Phytochemicals from African eggplants (Solanum macrocarpon L) and Black nightshade (Solanum nigrum L) leaves as acetylcholinesterase inhibitors: an in-silico study

Acetylcholinesterase inhibitors (AChEIs) like donepezil are commonly used to treat Alzheimer’s disease. AChEIs have also been considered for other therapeutic uses, such as anti-inflammatory neuroprotective agents. Consequently, the use of natural plant products as potential AChEIs can have therapeutic benefits. We previously reported the anticholinesterase properties of the phenolics and alkaloids found in the leaf extracts of two tropical plants with nutritional and ethnobotanical importance—African eggplant (Solanum macrocarpon L) and Black nightshade (Solanum nigrum L). Here, we tested the ability of both extracts to inhibit human erythrocyte AChE (an indirect mediator of pro-inflammatory cytokines production via acetylcholine degradation). We further used molecular docking and MD simulation to identify the potential molecular mechanism(s) of phenolic and alkaloid compounds as human AChEIs. Special focus was given to compounds containing the benzyl group that can establish stacking interactions similar to donepezil (a standard AChEI). Flavone-luteolin rutinosides (LR) were identified as single-binding or dual-binding AChEIs; specifically, we attributed the dual-binding LR4 and LR5 to their linked hexose moiety. This characteristic allows the dual binders to occupy the catalytic triads and the peripheral anionic subsite, while exploring the catalytic gorge. We further delineated the inhibition of human erythrocyte AChE, as the flavone common to both plant extracts—luteolin rutinosides—had positive in silico interactions with AChE. These findings suggest that phytochemicals from S. macrocarpon and S. nigrum with dual binding properties can be potential AChE inhibitors. In fact, compounds such as LR4 and LR5 should be further investigated as potential inhibitors of human AChE and may represent important natural alternatives to donepezil. Communicated by Ramaswamy H. Sarma

Design, Synthesis, DFT, Molecular Docking, and Biological Evalution of Pyrazole Derivatives as Potent Acetyl Cholinestrease Inhibitors

Alzheimer's disease (AD) is an age-related chronic and progressive neurodegenerative disease, affecting cognition, memory, and behavior. Treatment of Alzheimer's disease's (AD) symptoms has been done in several viable therapeutic ways; one of them is enhancing the neurotransmissions in the nervous system, such as acetylcholine. Acetylcholine is hydrolyzed into acetate and choline by acetylcholinesterase (AChE). In order to delay the hydrolysis of acetylcholine to take its transmission rule; AChE inhibitors were used to prevent the fast hydrolysis of acetylcholine by interacting with the enzyme rather than acetylcholine. In light of that, a new series of pyrazole molecules were synthesised and examined as potential AchE inhibitors. The target pyrazole compounds were synthesised from the reaction of formyl furan derivatives with acetophenone to give chalcone, followed by reaction with hydrazinehydrate and condensation with different aldehydes. The purified pyrazole derivatives were in-vitro screened for their acetyl cholinesterase (AChE) inhibitory activities using Ellman's method. The pyrazole derivative containing benzylidene moiety inhibited the AChE enzyme with an IC50 value of 5.28 M. Molecular docking studies were performed to test their activities against AchE. The density functional theory (DFT) calculations were performed to estimate the thermal parameters, dipole moment, polarizability, chemical reactivity descriptors, and molecular electrostatic potential of the prepared pyrazoline at the B3LYP/6-311G level of theory.

Bioactive sulfonyl hydrazones with alkyl derivative: Characterization, ADME properties, molecular docking studies and investigation of inhibition on choline esterase enzymes for the diagnosis of Alzheimer's disease

In this work, new sulfonylhydrazone compounds with alkyl derivatives (SH1– SH4 series) were synthesized via a green chemistry method, and their inhibition effects on acetylcholinesterase and butyrylcholinesterase (AChE, BChE) were determined in vitro. This work was designed in two stages; in the first stage, using compounds that contain both sulfonamide and hydrazine groups which have important pharmacological properties, a series of sulfonyl hydrazone with alkyl derivatives (SH1– SH4) were synthesized with a method that is less time-consuming and more environmentalist that was by using different substitute groups containing aldehyde and ketone compounds. The structures of the synthesized compounds were characterized by elemental analyses, 1H NMR, 13C NMR, FT-IR methods. In the second stage, the effects of the synthesized sulfonyl hydrazones with alkyl derivatives on acetylcholinesterase and butyrylcholinesterase enzymes were examined. According to the results, all the synthesized compounds inhibited AChE and BChE enzymes. When the IC50 values were compared, SH2-3 (IC50 = 5.27 ± 0.05 μM) and SH3-3 (IC50 = 12.29 ± 1.47 μM) compounds which are containing the butyl group have the best inhibition effect on the AChE enzyme and BChE enzyme, respectively. In addition, the predictive properties of all compounds in terms of drug similarity were scanned using five Lipinski rules and ADME estimations. In silico ADME studies play an important role in improving and predicting drug compounds. In the ADME study; The absorption, distribution, metabolism, elimination, and properties of the molecules given below were theoretically calculated. Also, to evaluate the binding interactions between the sulfonylhydrazone compounds and enzymes, molecular docking studies were performed and the compounds with the best inhibition effect SH2-3 (for AChE enzyme) and SH3-3 (for BChE enzyme) were tested. Both in vitro and silico the results showed that two compounds could act as potent inhibitors of AChE, BChE.

In-depth phytochemical and biological studies on potential AChE inhibitors in red and zigzag clover dry extracts using reversed–phase liquid chromatography (RP-LC) coupled with photodiode array (PDA) and electron spray ionization-quadrupole/time of flight-mass spectrometric (ESI-QToF/MS-MS) detection and thin-layer chromatography-bioautography

In the study, Trifolium medium L. and T. pratense L. were used to obtain lyophilisates which were named as TML and TPL, respectively. The former clover taxon represents a little explored species, while the latter one is often found in dietary supplements and functional foods due to the content of isoflavones that alleviate various menopausal symptoms. Detailed phytochemical profiles of both lyophilisates were examined and compared using coupled chromatographic (RP-LC) and spectroscopic PDA/ESI-QToF/MS-MS methods. A total of 54 and 55 compounds were identified in TML and TPL, respectively. Close chemotaxonomic similarities were confirmed for both clover taxa examined, especially in terms of the most abundant isoflavones and hydroxycinnamates. For the first time, neurotropic polyphenols (AChE inhibitors) were identified in clover extracts using TLC-bioautography. In this group, caffeoylmalic acid exhibited significant AChE inhibitory effect confirming the potential of TPL and TML to support physiological functions of the endocrine and nervous systems.

In vivo Evaluation of a Newly Synthesized Acetylcholinesterase Inhibitor in a Transgenic Drosophila Model of Alzheimer's Disease.

Alzheimer’s disease is a neurodegenerative disease characterized by disrupted memory, learning functions, reduced life expectancy, and locomotor dysfunction, as a result of the accumulation and aggregation of amyloid peptides that cause neuronal damage in neuronal circuits. In the current study, we exploited a transgenic Drosophila melanogaster line, expressing amyloid-β peptides to investigate the efficacy of a newly synthesized acetylcholinesterase inhibitor, named XJP-1, as a potential AD therapy. Behavioral assays and confocal microscopy were used to characterize the drug effect on AD symptomatology and amyloid peptide deposition. The symptomatology induced in this particular transgenic model recapitulates the scenario observed in human AD patients, showing a shortened lifespan and reduced locomotor functions, along with a significant accumulation of amyloid plaques in the brain. XJP-1 treatment resulted in a significant improvement of AD symptoms and a reduction of amyloid plaques by diminishing the amyloid aggregation rate. In comparison with clinically effective AD drugs, our results demonstrated that XJP-1 has similar effects on AD symptomatology, but at 10 times lower drug concentration than donepezil. It also showed an earlier beneficial effect on the reduction of amyloid plaques at 10 days after drug treatment, as observed for donepezil at 20 days, while the other drugs tested have no such effect. As a novel and potent AChE inhibitor, our study demonstrates that inhibition of the enzyme AChE by XJP-1 treatment improves the amyloid-induced symptomatology in Drosophila, by reducing the number of amyloid plaques within the fruit fly CNS. Thus, compound XJP-1 has the therapeutic potential to be further investigated for the treatment of AD.

Synthesis, characterization, molecular docking and in vitro screening of new metal complexes with coumarin Schiff base as anticholine esterase and antipancreatic cholesterol esterase agents

In this work, Combining coumarin and thiazole with 3-tertiary butyl salicylaldehyde into in a single molecule, new Schiff base (CTS), and its metal complexes with palladium and platinum were synthesized and characterized by using well-known spectroscopic techniques such as 1H-NMR, 13C-NMR, FT-IR and LC-MS. And also, the formation of these complexes were confirmed by magnetic moment and conductivity measurements. The photophysical properties of CTS were studied and it was observed that the Schiff base has a sensitivity to CN−, F−, and AcO− anions. The quantum chemical calculations based on density functional theory (DFT) were done for explaining some experimental, structural, and spectroscopic data of the dyes. Also, to evaluate the binding interactions between the ligand (CTS) and its metal complexes and enzymes, molecular docking studies were performed and all the compounds tested to determine its inhibition potential against the cholinesterase (AChE and BChE) and pancreatic cholesterol esterase (CEase) enzymes. Both in vitro and in silico the results showed that all of the compounds could act as potent inhibitors of AChE, BChE, and CEase. The Pt (II) complex showed the most potent inhibitory property against all of the enzymes with IC50 values of 12 µM for AChE, 23 µM for BChE, and 21 µM for CEase. Communicated by Ramaswamy H. Sarma

Novel Iodinated Hydrazide-hydrazones and their Analogues as Acetyl- and Butyrylcholinesterase Inhibitors.

Hydrazide-hydrazones have been known as scaffold with various biological activities including inhibition of acetyl- (AChE) and butyrylcholinesterase (BuChE). Cholinesterase inhibitors are mainstays of dementias' treatment. Twenty-five iodinated hydrazide-hydrazones and their analogues were designed as potential central AChE and BuChE inhibitors. Hydrazide-hydrazones were synthesized from 4-substituted benzohydrazides and 2-/4- hydroxy-3,5-diiodobenzaldehydes. The compounds were investigated in vitro for their potency to inhibit AChE from electric eel and BuChE from equine serum using Ellman's method. We calculated also physicochemical and structural parameters for CNS delivery. The derivatives exhibited a moderate dual inhibition with IC50 values ranging from 15.1-140.5 and 35.5 to 170.5 μmol.L-1 for AChE and BuChE, respectively. Generally, the compounds produced a balanced or more potent inhibition of AChE. N'-[(E)-(4-Hydroxy-3,5-diiodophenyl)methylidene]-4- nitrobenzohydrazide 2k and 4-fluoro-N'-(2-hydroxy-3,5-diiodobenzyl)benzohydrazide 3a were the most potent inhibitors of AChE and BuChE, respectively. Structure-activity relationships were established, and molecular docking studies confirmed interaction with enzymes. Many novel hydrazide-hydrazones showed lower IC50 values than rivastigmine against AChE and some of them were comparable for BuChE to this drug used for the treatment of dementia. They interact with cholinesterases via non-covalent binding into the active site. Based on the BOILEDEgg approach, the majority of the derivatives met the criteria for blood-brain-barrier permeability.

Acylphloroglucinols with acetylcholinesterase inhibitory effects from the fruits of Eucalyptus robusta

Eleven new acylphloroglucinols, including six new formylated phloroglucinol-monoterpene meroterpenoids, eucalyprobusals A–F (1–6), one monomeric acylphloroglucinol, eucalyprobusone B (7), and four dimeric acylphloroglucinols, eucalyprobusones C–F (8–11) were purified from the fruits of Eucalyptus robusta. The establishment of the structures of 1–11 was achieved by a combination of NMR and HRESIMS data analyses, electron circular dichroism (ECD), and single-crystal X-ray diffraction. Compounds 6, 8, and an inseparable mixture of 10 and 11 were found to be potent AChE inhibitors with IC50 values of 3.22 ± 0.36, 3.82 ± 0.22, and 2.55 ± 0.28 μΜ, respectively. Possible interaction sites of 6, 8, 10, and 11 with AChE were investigated by means of molecular docking studies, and the results revealed that AChE residues Asn87, Ser125, Thr83, Tyr133, Tyr124, Tyr337, and Tyr341 played crucial roles in the observed activity of the aforementioned compounds.

Synthesis of Novel 2,3-Dihydro-5,6-dimethoxy-2-((piperidin-4-yl)methyl) inden-1-one Derivatives as Acetyl Cholinesterase Inhibitors

Background: Novel carboxamides and thioureas of 2,3-dihydro-5,6-dimethoxy-2-((piperidin- 4-yl)methyl) inden-1-one were synthesized and their potential anticholinesterase activities were evaluated. The inhibition potency of the compounds 17a-j and 19a-j against AChE was measured and evaluated using Ellman’s spectrophotometric method. Among carboxamides series, compound 17f, 17i, 17j and among thiourea series, compound 19a, 19b were found to be the most active. Methods: The scaffold 2,3-dihydro-5,6-dimethoxy-2-((piperidin-4-yl)methyl) inden-1-one 16, key intermediate of drug donepezil has been synthesised in three steps and derivatised as carboxamides and thioureas for SAR studies. Compounds 17a-j and 19a-j were characterised by 1H NMR and LCMS. The inhibitory activity and antiamnesic effect were studied using different sources such as electric eel AChE, human serum AChE and rat brain homogenate AChE. Results: The results of bioassays indicated that among all the synthesized compounds tested, five compounds 17f, 17i, 17j, 19a and 19b shows IC50 at a dose of 67, 42, 64, 52 and 63 nM respectively against electric eel, human serum and rat brain homogenate, which lead to the suggestion that compound 17i might be considered to be a potent AChE inhibitor. Conclusion: Derivatives of 2,3-dihydro-5,6-dimethoxy-2-((piperidin-4-yl)methyl)inden-1-one with different substitutions were synthesised and tested for their AChE activity. The order of potency is 17i>17j>17f and 19a>19b. The other compounds screened failed to elicit any inhibition of acetyl cholinesterase from rat brain homogenate. It may be concluded from this study that, for effective binding and blocking the AChE activity, molecule needs to bind with peripheral site and active site of the enzyme. Therefore, it can be summarized that by changing the functional group and substitution in the scaffold 2,3-dihydro-5,6-dimethoxy-2-((piperidin-4-yl)methyl)inden-1-one needs to be studied for better AChE inhibitory activity in future research.

Development of novel carbazole derivatives with effective multifunctional action against Alzheimer’s diseases: Design, synthesis, in silico, in vitro and in vivo investigation

Carbazole based novel multifunctional agents has been rationally designed and synthesized as potential anti-Alzheimer agents. Multi-functional activity of these derivatives have been assessed by performing various in-vitro assays and these compounds appeared to be potent AChE inhibitors, Aβ aggregation inhibitors, anti-oxidant and neuroprotective agents. Among the entire series, MT-1 and MT-6 were most potent multifunctional agents which displayed effective and selective AChE inhibition, Aβ disaggregation, anti-oxidant and metal chelation action. Neuroprotective activity of MT-6 has been examined against H2O2 induced toxicity in SHSY-5Y cells and they have shown effective neuroprotection. Additionally, MT-6 did not display any significant toxicity in SHSY-5Y cells, indicating its non-toxic nature. Molecular docking and MD simulation studies have been also performed to explore molecular level interaction with AChE and Aβ. Finally, MT-6 was evaluated against scopolamine induced dementia model of mice and this compound actively improved memory deficit and cognition impairment in scopolamine treated mice. Thus, novel carbazole derivative MT-6 has been explored as an effective and safe multifunctional agent against AD and this molecule may be used as a suitable lead for development of effective anti-Alzheimer agents in future.

Molecular docking and investigation of 4-(benzylideneamino)- and 4-(benzylamino)-benzenesulfonamide derivatives as potent AChE inhibitors

The discovery of acetylcholinesterase inhibitors is important for the treatment of Alzheimer’s disease (AD), known as the most common type of dementia. Due to the side effects of commonly used acetylcholinesterase inhibitors, studies for the detection of new inhibitors are increasing day by day. In this study, we investigated the effects of some sulfonamide derivatives (S1–S4 and S1i–S4i) on AChE enzymes. The best pose of the active compounds to understand the mechanism of possible inhibition in interaction of enzyme-sulfonamide derivative were performed docking studies after in vitro experimental results. ADME-related physicochemical and pharmacokinetic properties of the synthesized 4-aminobenzenesulfonamide derivatives were the compatibility with Lipinski’s rule of five. We found that the synthesized derivatives of sulfonamides show potential inhibitor properties for AChE with Ki constants in the range of 2.54 ± 0.22–299.60 ± 8.73 µM. The derivatives of sulfonamides exhibited different inhibition type. We determined that the derivatives (S1, S1i, S3, and S3i) showed a competitive inhibition effect, whereas others (S2, S2i, S4, and S4i) showed mixed-type inhibition. As a result, the sulfonamide derivatives can be used as an alternative acetylcholinesterase inhibitor due to this effect. Inhibitors with fewer side effects, are thought to be important in the treatment of AD.

Enantioselective Fluorocyclizations Mediated by Amino‐Acid‐Derived Phthalazine

AbstractNovel amino‐acid‐derived phthalazine reagents have been designed and synthesized for the enantioselective fluorocyclizations of prochiral indoles. The scope of reaction is evidenced by 28 examples of fluorinated furoindole and pyrroloindole heterocycles bearing various functionalities with up to 99% ee. The resulting enantioenriched fluorinated products are found to be potent AChE inhibitors. Advantages of the current new chiral reagents include ease in the synthesis of analogues and readily tunable steric/electronic demands.magnified image

Neurobehavioral investigation and acetylcholinesterase inhibitory activity study for some new coumarin derivatives

Twenty four 6-aminocoumarin based derivatives were synthesized according to two schemes. All the compounds were screened for their acetylcholinesterase inhibitory activity where compound 5b proved to be the most potent AChE inhibitor with (IC50 = 37 nM) compared to tacrine and donepezil (IC50 = 55.0 and 59.0 nM, respectively). Six compounds 2f, 2g, 4b, 5b, 8b and 9b revealed superior activity over donepezil and a conclusive structure activity relationship study was conducted explaining the obtained results. Furthermore, compounds 2f, 4b and 5b were investigated for their neurobehavioral effect in vivo. All the tested compounds showed improvement of neurobehavioral experiments using donepezil as reference drug. In addition, compounds 2f, 4b and 5b were able to reduce extracellular deposition of amyloid beta 42 in a comparable manner to donepezil. The binding modes of the synthesized compounds were evaluated in silico via molecular docking in the active site of AChE, as well as molecular dynamics simulation study. A pharmacophore model was generated for the newly synthesized compounds.

Effect of Salvia miltiorrhiza on acetylcholinesterase: Enzyme kinetics and interaction mechanism merging with molecular docking analysis

Acetylcholinesterase (AchE) serves as an important target for Alzheimer's disease. Salvia miltiorrhiza has been used to treat cardiovascular disease for hundreds of years. However, the interaction between S. miltiorrhiza and AchE is still inadequate. Herein, an integrated method including molecular docking and experimental studies was employed to investigate the interaction. Consequently, some components were screened as potent AchE inhibitors by in silico and in vitro. Among them, miltirone (MT) and salvianolic acid A (SAA) reversibly inhibited AchE in a mixed-competitive manner. Fluorescence data revealed that SAA and salvianolic acid C (SAC) strongly quenched the intrinsic fluorescence of AchE through a static quenching mechanism, and the binding was spontaneous and dominated by hydrophobic interaction inferred by the thermodynamic parameters. The synchronous and ANS-binding fluorescence spectra suggested that SAA and SAC could bind to the enzyme and induce its conformation changes of secondary structures, which was further confirmed by Fourier transform infrared spectra. Meanwhile, molecular docking presented the probable binding modes of inhibitors to AchE and highlighted the key role of hydrophobic interaction and hydrogen bonds for the stability of docking complex. These findings put more insights into understanding the interaction of S. miltiorrhiza chemicals and AchE, as well as Alzheimer's disease.

Synthesis and AChE-Inhibitory Activity of New Benzimidazole Derivatives.

Alzheimer’s disease (AD), one of the main causes of aged dementia, is a progressive and degenerative neurological disorder characterized by loss of cognition and memory. Although the symptomatic treatment of AD, particularly acetylcholinesterase inhibitors (AChEIs) based on the ‘cholinergic hypothesis’, has been successful in clinic, at present there is no cure for this disease. In this study, we designed compounds carrying benzimidazole and triazole rings on the same chemical skeleton so as to investigate their potential acetylcholinesterase and butyrylcholinesterase activity. Furthermore, molecular modeling study was performed to determine the binding mode of the best inhibitor to the AChE. Among them, compounds 3d and 3h, which featured 3,4-dihydroxy substitution at the phenyl ring and 5(6)-chloro substitution at the benzimidazole ring were found to be potent inhibitors of AChE. The inhibition kinetics of the two most active derivatives 3d and 3h were further studied. The kinetic displayed increasing slope and increasing intercept, which is consistent with a mixed inhibition. The IC50 and Ki values of 3d are 31.9 ± 0.1 nM and 26.2 nM, respectively. Compound 3h exhibited IC50 of 29.5 ± 1.2 nM and Ki of 24.8 nM. The above data compared favorably with data for donepezil (21.8 ± 0.9 nM) the reference compound in our study.